Developments in the cross-country ski sport in recent years have resulted in the use of steadily more lightweight ski equipment including lighter weight shoes, skis and bindings.
In regard to soles for cross-country ski shoes, the use of leather is being replaced by synthetic materials such as rubber and plastics, for example nylon. Toe bindings of various types have been made lightweight and smaller, particularly in connection with the development of so-called "snabel" or "nose tip shoes", where an extremity or nose on the shoe sole is locked into the toe binding.
These developments have resulted in lightweight and comfortable equipment, particularly for competition skiers. However, these developments have simultaneously resulted in steadily greater problems in obtaining a dependable and torque-stable connection between the shoe and the ski such that lateral movements of the shoe in the binding and also of the shoe itself are avoided. Such lateral movements result because the heel portion of the shoe becomes more or less displaced from its support on the ski, resulting in unstable and uncomfortable skiing. In order to avoid this shortcoming, attempts have been made to develop better toe bindings and various forms of heel support in order to hinder such lateral displacement of the shoe. The need for steady support of the shoe on the ski is even more important because of the use of present day narrow and lighter skis and very lightweight and thin cross-country shoes, frequently made from a more or less elastic textile material.
Many different solutions have been proposed to improve biasing support and locking of the shoe onto the ski. For example, the front of the sole of the shoe is locked into a toe binding which includes a clamp, side ears or walls and upwardly extending pins. The tip or toe extension of the sole is placed between the side walls, the pins extend into apertures in the toe extension and the clamp secures the toe extension in position. Currently several types of commercial bindings which are adapted to receive a standardized sole are available. However, special types of commercial bindings are also available. Further, various types of heel supports are currently in use. One type of heel support uses V-shaped groove in the heel of the sole which fits around a complementary V-shaped projection attached to the ski. In another prior art technique, crosswise or longitudinally extending grooves or the like are formed in the surface of the sole between toe and heel. Norwegian Pat. No. 140 325 discloses a cross-country ski shoe sole provided with a pair of longitudinal grooves or ridges adapted to receive opposed side edges of the ski. These grooves or ridges are located in the forefoot section of the sole.